I would be VERY wary of any medication off the internet! And would never use on my children!
As to the headlice, the eggs (nits) are fixed near the scalp. Dark, plump ones are 'live' and will hatch into lice. These need to be removed - either manually or with a nit comb.
White, flat ones are empty cases or non viable eggs and will not produce a live louse but I would still remove, just to be sure and also as doesn't look good!
The nearer the eggs are to the scalp, the fresher/younger they are. Further down the hairshaft and they are older or previous infestation.
Need to wet comb with conditioner or oil to remove the nits before they hatch and reinfest. I usually do every other day when I have found live lice. Lots of conditioner and cream coloured plastic nit comb works for me. (Found the metal ones dragged the hair and didn't like them)
The next day, I sit with child with white sheet or towel round their shoulders and go through with my magnifying glasses and pick out the nits (and any live lice) I come across. (Put on a DVD for DC). This way I can see the scale of the infestation and work out how long they have been there. Then I know if is a recent one or longer and how much effort I will have to put in to clear it. Usually find most behind the ears or back of crown for some reason.
I also nit comb regularly each time I wash their hair - this way, I can catch the infestation early, before they have had time to lay many eggs.
Always nit comb at end of term and beginning of new term - that way you know if has been picked up from school or family!
I am not too bothered about it now as I know how to clear them (and haven't had any for the past year) but used to p* me off no end when they got them as I couldn't rest until I had cleared them! Only used chemicals the first time and didn't work so resorted to time honoured methods.
HTH and GOOD LUCK!